Copper chromium magnesium alloy



Patented June 27, 1939 UNITED fsTATEs PATENT OFFICE COPPER CHROMIUM MAGNESIUM ALLOY Application September 15, 1937, Serial No. 164,033

3 Claims.

This invention relates to alloys, and more particularly to copper alloys of improved characteristics.

An object of the invention is to produce an improved copper base alloy.

Another object is to produce a copper magnesium alloy, which is highly susceptible to age hardening and work hardening.

p Another object is to provide an alloy of high hardness, coupled with improved electrical and thermal characteristics.

Other objects of the invention will be apparent from the following description taken in connection with the appended claims.

5 The present invention comprises the combination of elements, methods of manufacture and the product thereof, brought out and exemplified in the disclosure hereinafter set forth, the scope of the invention being indicated in the appended claims.

In the drawing:

Figures 1 and 3 are graphs showing curves illustrating the improvement in the hardness and electrical conductivity of alloys of the present invention during age hardening.

Figures 2 and 4 are graphs showing the effect of cold working on these alloys after age hardening.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may 'be made in the method of procedure and the combination of elements without departing from the spirit of the invention.

a The invention relates to alloys of copper, magnesium and chromium. While these alloys may vary in their physical characteristics with the type of treatment received and the proportions of various ingredients, they will generally be characterized by high conductivity and hardness and by heat resistance.

According to the preferred method of carrying out our present invention, an alloy is made' containing copper, magnesiumand chromium in substantially the following proportions:

l5 Per cent Magnesium 0.1-3 Chromium 0.1-3 Copper Balance 50 It is possible, likewise, to improve the alloys consisting primarily of the alloy described above, but also containing small percentages of additional ingredients, such as silver, zinc, cadmium, calcium, lithium, silicon, titanium and beryllium.

55 In .carrying out the present invention, a copper (Cl. 'l5-153) a pressed product or a pressed and sintered prod,-I

uct or a melted product. In order to get the chromium completely in solution into the' copper, it is necessary to keep the melt at an elevated temperature for some time. The magnesium is preferably added also in the form of a hardener alloy.

Magnesium will act, in addition to its function as an alloying ingredient, as a very strong deoxidizer and therefore with this new combination of copper magnesium chromium, it is possible to produce very sound castings.

After the alloy has been prepared according to such alloying methodsA` as described above the heat treament may be carried out as follows: The alloy, in the form of a billet or a sand casting, or any other form, is raised in temperature to 700 degrees C. and preferably to a temperature in the order of 800-1000 degrees C. The alloy is then quenched from `this high temperature and subsequently aged at a temperature below r100 degrees C. and preferably in the range between 400 and 600 degrees C. This heat treatment results in considerable improvement in the hardness of the alloy.

An example of an alloy of the present invention is one containing- Per cent Chromium 0.63 Magnesium 0.45 Copper Balance Per cent Chromium 0.42 Magnesium 0.90 Copper Balance Per cent Chromium 0.25 Magnesium 0,42 Copper Balance reached a hardness of 66 Rockwell B after aging. With 25% reduction by cold working a Rockwell B hardness of 81 was obtained and after 65% cold work the hardness was further increased to `85 Rockwell B. At the same time the electrical conductivity was of that of pure copper.

The effect `of magnesium is very pronounced as far as its cold working is concerned, and with higher percentagesof magnesium, higher ultimate hardness will be reached. Thiscan not be accomplished with binary alloys containing only copper and chromium.

We have also found that these alloys are very well suited for treatments in which the various steps of heat hardening and work hardening are combined in various manners. For instance, the alloy may be quenched rst, then cold worked, then aged and again cold Worked. Another remarkable effect of the heat treatment is the great improvement 'in -the electrical conductivity.V With some alloy combinations Within the percentage range given above, conductivities rangingfrom 55.-.75% ofvthat of pure copper can'be easily obtained. The improvements in the conductivities of the first two example alloys are shown in Figures 1 and 3.

While it is possible to obtain 'o romy good combination of hardness andconductivity in binary copper chromium alloys, provided that high enough percentages ofv chromium are added, we have found .that by decreasing the chromium content and adding a larger percentage of magnesium, much f higher hardnesses are reached than can ever be obtained in binary combinations.

z 'I'he alloy, on account of these outstanding physical properties,.is well suited for use at comparatively high temperatures, since the hardness and electrical conductivity are maintained for indeiihite periods at the aging temperatures indicated.

The alloys prepared as indicated above are well suited for the manufacture of any type of castings, such as sand castings, chill castings and permanent mold castings. The alloys are further well suited for such manufacturing processes as workingare'also highly resistant to abrasion.

They have high fatigue limits and good spring properties and can therefore be used for current carrying or heat carrying springs. l

Another important use 'of these high strength alloys is in the manufacturing of cylinder heads, pistons and other parts of internal combustion engines, such as automobile engines, where high heat conductivity is needed.

While the present invention, as to its objects and advantages has been described herein as carried out in specific embodiments thereof,.it is not desired to be limited thereby, but it is intended to cover the invention broadly within the spirit'andscope of the appended claims.

What is claimed is:

1. An alloy containing 0.1-3% magnesium, 0.143% chromium, and the balance copper.

2. A hardened alloy composed of about 0.13% magnesium, 0.1-3% chromium and the balance substantiallly all copper, characterized by a combination of high hardness and high electrical and alloying constituents.

FRANZ R. HENSEL EARL I.v LARSEN. 

